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1.
Sci Rep ; 13(1): 21353, 2023 12 04.
Article in English | MEDLINE | ID: mdl-38049468

ABSTRACT

While earlier investigations into thermal perception focused on measuring the detection of temperature changes across distinct bodily regions, the complex nature of thermal perception throughout the entire body remains a subject of ongoing exploration. To address this, we performed an experiment using four climate chambers with oscillating temperatures between 24 °C ± 1 °C. Our study involved 26 participants who moved between these chambers and had the task of reporting whether the second chamber entered was warmer or colder than the previous one. We collected 3120 temperature judgments, which we analysed via generalised linear mixed-effects models. The results showed surprisingly accurate temperature discrimination abilities and limited variation between individuals. Specifically, the Point of Subjective Equality stood at - 0.13 °C (± 0.02 °C), the Just Noticeable Difference (JND) was 0.38 °C (± 0.02 °C), the JND95 (indicating 95% accuracy) 0.92 °C (± 0.05 °C), the negative ceiling performance level (CPL) was - 0.91 °C (± 0.28 °C) and the positive CPL 0.80 °C (± 0.34 °C). The implications of the JND95 and the CPLs are particularly noteworthy, as they hold potential to significantly contribute to the advancement of intelligent algorithms for temperature control systems within building environments.


Subject(s)
Climate , Cold Temperature , Humans , Temperature , Linear Models , Judgment
3.
Q J Exp Psychol (Hove) ; 76(6): 1209-1219, 2023 Jun.
Article in English | MEDLINE | ID: mdl-35866345

ABSTRACT

Olfactory perception can be modulated by the repeated exposure to odours. Olfactory habituation is a reduced behavioural response to repetitive stimulation. Edibility is considered an important top-down feature that can affect olfactory perception, but whether it could modulate olfactory habituation when food or nonfood odours are repeatedly smelled remains unclear. Indeed, due to their ecological salience, food odours attract attention automatically which might slow down habituation. This registered report aimed to determine whether olfactory habituation shows a different pattern when participants are presented with food or nonfood odours. In a within-subject design, 50 participants were tested under satiated and fasted states in separated experimental sessions. In each session, participants were exposed to the same food and nonfood odour in different blocks of 20 trials each. Participants rated the perceived odour intensity and pleasantness after each trial. We used an intermittent odour presentation to reduce olfactory fatigue while capitalising on the effect of cognitive states on habituation. Linear mixed-effects models showed that the perceived odour intensity decreased over time only for nonfood odours. Conversely, the perceived odour pleasantness decreased significantly more across trials for food odours. These effects were retrieved regardless of the participant's hunger state. Our results are in line with the olfactory-specific satiety theory which posits a specific decrease in the perceived pleasantness of food odours, without changes in the perceived odour intensity. In short, our findings indicate that perceived odour edibility modulates olfactory habituation, extending the previous literature on the impact of top-down factors on olfactory perception.


Subject(s)
Odorants , Olfactory Perception , Humans , Olfactory Perception/physiology , Emotions/physiology , Smell/physiology
4.
Life (Basel) ; 12(10)2022 Sep 25.
Article in English | MEDLINE | ID: mdl-36294922

ABSTRACT

Chemosensory dysfunction is a frequent postacute sequela of COVID-19. Depending on the type of test used to measure it (self-report vs. direct test), the degree of chemosensory dysfunction in long-term COVID-19 has been found to be highly variable. In this manuscript, we report the cross-sectional data (first assessment) of a longitudinal study (6-month follow-up) examining smell, taste, and chemesthesis in participants affected by long-term COVID-19 (COVID+) and participants without COVID-19 (COVID-) by means of both self-reported and direct psychophysical methods. In total, 208 Italian participants (COVID+ n = 133; COVID- n = 75) completed the Smell and Taste Check developed by the Global Consortium for Chemosensory Research (GCCR), which includes self-reports on smell, taste, and chemesthetic abilities as well as direct intensity ratings of unstandardized smell, taste, and chemesthetic household items. Furthermore, all participants completed SCENTinel, a validated direct smell test. We found a positive association between the self-reported, unstandardized direct test and the validated direct test for smell, indicating moderate to large agreement across measures. Furthermore, the performance on SCENTinel was significantly associated with self-reported smell loss. A positive association between the self-reports and the intensity of household items was also retrieved for taste and chemesthesis. The time relative to COVID-19 onset (267.3 ± 113.9 days) did not modulate the chemosensory performance of self-reported abilities, intensity ratings, and SCENTinel. All in all, we confirm the impairment of three chemical senses (smell, taste, and chemesthesis) in an independent sample of Italian participants affected by long-term COVID-19 by using and comparing self-reported and direct psychophysical methods. We contribute to the discussion on best practices to monitor chemosensory dysfunction in individuals affected by long-term COVID-19.

5.
Exp Brain Res ; 239(12): 3417-3429, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34536083

ABSTRACT

Previous research about body size estimation in obesity reported heterogeneous results. This might be related to the fact that the tasks adopted explored different body representations. Classifying the previous studies according to the specific body representation probed (i.e. implicit, explicit or both) might clarify discordant findings. A systematic review and meta-analysis of research articles assessing body size estimation in individuals affected by obesity compared with healthy weight individuals were performed in PubMed and Web of Science. Additional records were identified by reference lists inspection. The last search was run in May 2021. Two independent authors performed data extraction according to predefined criteria. Both groups either overestimated or underestimated the implicit body representation depending on the task used and the body part considered. Conversely, the explicit representation of the body was mainly overestimated by both individuals with obesity and healthy weight. In tasks relying on both these representations, overestimation and underestimation were reported in both groups, possibly depending on the degree of which each procedure relied on the explicit and/or implicit representation of the body. According to the meta-analysis, individuals with obesity tended to be significantly less accurate in body size estimations than participants with healthy weight. We confirmed that heterogeneous findings in body size estimation in obesity are related to the adoption of different tasks, which likely involve different body representations. We discussed the role of body dissatisfaction and altered somatosensation in the lower accuracy observed in obesity.


Subject(s)
Body Image , Obesity , Body Size , Human Body , Humans
6.
Cortex ; 142: 1-14, 2021 09.
Article in English | MEDLINE | ID: mdl-34166922

ABSTRACT

Voluntary actions are accompanied by the experience of controlling one's own movements (sense of agency) and the feeling that the moving body part belongs to one's self (sense of body ownership). So far, agency and body ownership have been investigated separately, leaving the neural underpinnings of the relation between the two largely unexplored. The aim of this study was to explore the causal role of two multisensory brain regions, that is the premotor cortex (PMc) and the cerebellum, in agency and body ownership concurrently on the same behavioral task, i.e., the moving Rubber Hand Illusion (mRHI). Participants watched a rubber hand while moving their hidden hand. The type of movement (active or passive) and posture of the rubber hand (congruent or incongruent) differed in three conditions (active congruent, passive congruent, active incongruent), so that agency and ownership could be elicited either separately or concurrently. Agency and ownership were measured by subjective report and proprioceptive drift. Sham and anodal transcranial direct current stimulation (tDCS) were delivered to the PMc (Experiment 1) or the cerebellum (Experiment 2) prior to the mRHI task. Independent of the site or type of tDCS, subjective reports revealed that both agency and ownership were evoked in the active congruent condition, ownership but not agency in the passive congruent condition, and agency but not ownership in the active incongruent condition. The proprioceptive drift was evoked in the active congruent and the passive congruent condition. Anodal tDCS over the PMc reduced the feeling of agency in the active congruent condition, while it enhanced proprioceptive drift when applied over the cerebellum. These findings suggest a specific causal contribution of the PMc and the cerebellum to bodily self-perception during voluntary movement, with the PMc mainly involved in awareness of action and the cerebellum in proprioceptive adaptation of body position in space.


Subject(s)
Motor Cortex , Touch Perception , Transcranial Direct Current Stimulation , Body Image , Cerebellum , Humans , Self Concept , Visual Perception
7.
Q J Exp Psychol (Hove) ; 74(6): 1103-1116, 2021 Jun.
Article in English | MEDLINE | ID: mdl-33327881

ABSTRACT

To locate our body in the space, we rely on an implicit representation of body size and shape: the body model. Evidence about the implicit representation of bodily dimensions in obesity is rare. Nevertheless, it seems to suggest that such representation is not altered in obesity compared to healthy weight individuals. To probe further this hypothesis, we investigated the implicit representation of hand dimensions with a landmark localisation task, comparing individuals with obesity and healthy weight individuals. Furthermore, as body model distortions may be related to tactile acuity, the tactile acuity threshold was measured using a two-point discrimination task. In accordance with the previous evidence, we observed that healthy weight participants showed a significant underestimation of finger length and overestimation of hand width. Interestingly, comparable body model distortions were shown also in participants with obesity. No differences in tactile acuity emerged between the two groups; also, when considering the whole sample, as tactile acuity decreases hand width overestimation increases. Thus, obesity seems to have no effect on the characteristics of the body model relative to the hand. Accordingly, the physiological mechanisms supporting the development of the implicit representation of hand dimensions in the healthy weight population may be preserved in obesity.


Subject(s)
Body Image , Touch Perception , Body Size , Hand , Humans , Obesity , Touch
8.
Article in English | MEDLINE | ID: mdl-32132905

ABSTRACT

Natural exploration of textures involves active sensing, i.e., voluntary movements of tactile sensors (e.g., human fingertips or rodent whiskers) across a target surface. Somatosensory input during moving tactile sensors varies according to both the movement and the surface texture. Combining motor and sensory information, the brain is capable of extracting textural features of the explored surface. Despite the ecological relevance of active sensing, psychophysical studies on active touch are largely missing. One reason for the lack of informative studies investigating active touch is the considerable challenge of assembling an appropriate experimental setup. A possible solution might be in the realm of virtual tactile reality that provides tactile finger stimulation depending on the position of the hand and the simulated texture of a target surface. In addition to rigorous behavioral studies, the investigation of the neuronal mechanisms of active tactile sensing in humans is highly warranted, requiring neurophysiological experiments using electroencephalography (EEG), magnetoencephalography (MEG) and/or functional magnetic resonance imaging (fMRI). However, current neuroimaging techniques impose specific requirements on the tactile stimulus delivery equipment in terms of compatibility with the neurophysiological methods being used. Here, we present a user-friendly, MEG compatible, tactile virtual reality simulator. The simulator consists of a piezo-electric tactile stimulator capable of independently protruding 16 plastic pistons of 1 mm diameter arranged in a 4 × 4 matrix. The stimulator delivers a spatial pattern of tactile stimuli to the tip of a finger depending on the position of the finger moving across a 2-dimensional plane. In order to demonstrate the functionality of the tactile virtual reality, we determined participants' detection thresholds in active and passive touch conditions. Thresholds in both conditions were higher than reported in the literature. It could well be that the processing of the piston-related stimulation was masked by the sensory input generated by placing the finger on the scanning probe. More so, the thresholds for both the active and passive tasks did not differ significantly. In further studies, the noise introduced by the stimulator in neuromagnetic recordings was quantified and somatosensory evoked fields for active and passive touch were recorded. Due to the compatibility of the stimulator with neuroimaging techniques such as MEG, and based on the feasibility to record somatosensory-related neuromagnetic brain activity the apparatus has immense potential for the exploration of the neural underpinnings of active tactile perception.

9.
Multisens Res ; 33(7): 777-791, 2020 08 18.
Article in English | MEDLINE | ID: mdl-31978872

ABSTRACT

Preliminary evidence showed a reduced temporal sensitivity (i.e., larger temporal binding window) to audiovisual asynchrony in obesity. Our aim was to extend this investigation to visuotactile stimuli, comparing individuals of healthy weight and with obesity in a simultaneity judgment task. We verified that individuals with obesity had a larger temporal binding window than healthy-weight individuals, meaning that they tend to integrate visuotactile stimuli over an extended range of stimulus onset asynchronies. We point out that our finding gives evidence in support of a more pervasive impairment of the temporal discrimination of co-occurrent stimuli, which might affect multisensory integration in obesity. We discuss our results referring to the possible role of atypical oscillatory neural activity and structural anomalies in affecting the perception of simultaneity between multisensory stimuli in obesity. Finally, we highlight the urgency of a deeper understanding of multisensory integration in obesity at least for two reasons. First, multisensory bodily illusions might be used to manipulate body dissatisfaction in obesity. Second, multisensory integration anomalies in obesity might lead to a dissimilar perception of food, encouraging overeating behaviours.


Subject(s)
Auditory Perception/physiology , Illusions/physiology , Judgment/physiology , Obesity/physiopathology , Reaction Time/physiology , Time Perception/physiology , Visual Perception/physiology , Acoustic Stimulation , Adult , Body Weight , Female , Healthy Volunteers , Humans , Male , Photic Stimulation
10.
Psychol Res ; 84(4): 932-949, 2020 Jun.
Article in English | MEDLINE | ID: mdl-30467818

ABSTRACT

The self-serving bias is the tendency to consider oneself in unrealistically positive terms. This phenomenon has been documented for body attractiveness, but it remains unclear to what extent it can also emerge for own body size perception. In the present study, we examined this issue in healthy young adults (45 females and 40 males), using two body size estimation (BSE) measures and taking into account inter-individual differences in eating disorder risk. Participants observed pictures of avatars, built from whole body photos of themselves or an unknown other matched for gender. Avatars were parametrically distorted along the thinness-heaviness dimension, and individualised by adding the head of the self or the other. In the first BSE task, participants indicated in each trial whether the seen avatar was thinner or fatter than themselves (or the other). In the second BSE task, participants chose the best representative body size for self and other from a set of avatars. Greater underestimation for self than other body size emerged in both tasks, comparably for women and men. Thinner bodies were also judged as more attractive, in line with standard of beauty in modern western society. Notably, this self-serving bias in BSE was stronger in people with low eating disorder risk. In sum, positive attitudes towards the self can extend to body size estimation in young adults, making own body size closer to the ideal body. We propose that this bias could play an adaptive role in preserving a positive body image.


Subject(s)
Body Image/psychology , Self Concept , Size Perception , Thinness , Beauty , Bias , Female , Humans , Male , Photic Stimulation , Young Adult
11.
Multisens Res ; 33(3): 337-361, 2020 07 01.
Article in English | MEDLINE | ID: mdl-31722290

ABSTRACT

The Rubber Hand Illusion (RHI) is used widely to investigate the multisensory integration mechanisms that support bodily self-consciousness and, more specifically, body ownership and self-location. It has been reported that individuals affected by obesity show anomalous multisensory integration processes. We propose that these obesity-induced changes could lead to an unusual susceptibility to the RHI and anomalous bodily self-experience. To test this hypothesis, we administered a modified version of the RHI (using a picture of the participant's hand) to individuals affected by obesity and participants with a healthy weight. During synchronous and asynchronous stimulation, we compared the subjective experience of the illusion (using a questionnaire) and the effect of the illusion on self-location (i.e., proprioceptive drift). In accordance with the illusion phenomenology, both groups had a comparable subjective illusory experience after the synchronous stimulation. Nevertheless, individuals affected by obesity showed less recalibration of self-location than healthy weight participants. In light of a recent interpretation of the multisensory integration mechanisms that underpin the RHI, our findings suggest that in obesity visuo-tactile integration supporting the subjective experience of the illusion is preserved, whereas visuo-proprioceptive integration for self-location is reduced.


Subject(s)
Dissociative Disorders/physiopathology , Hand/physiopathology , Illusions/physiology , Obesity/physiopathology , Proprioception/physiology , Touch Perception/physiology , Visual Perception/physiology , Adult , Dissociative Disorders/etiology , Emotions/physiology , Female , Humans , Male , Obesity/complications
12.
PLoS One ; 13(11): e0207528, 2018.
Article in English | MEDLINE | ID: mdl-30440038

ABSTRACT

How do age-related changes affect the sense of body ownership? This study tackles this issue by means of the rubber hand illusion (RHI), a widely used experimental tool for investigating the sense of body ownership. There is ample literature on the RHI in young populations, but research on age-related changes in the RHI is still scarce. Here we extend the use of the RHI to examine the changes in the sense of body ownership related to healthy aging. Subjective reports (i.e., questionnaire) and proprioceptive drift were compared among young (n = 22, age range 20-22 years), middle-aged (n = 22, age range 44-55 years), and older adults (n = 22, age range 60-72 years). A stronger subjective experience of illusion was observed in the young and older adults as compared to the middle-aged. No differences in proprioceptive drift were found between the three groups. These findings are discussed in relation to: 1) different stages of development of perceptual and cognitive components of the sense of body ownership, and 2) compensatory mechanisms.


Subject(s)
Hand/physiology , Touch Perception/physiology , Visual Perception/physiology , Adult , Aged , Female , Human Body , Humans , Illusions , Male , Middle Aged , Ownership , Surveys and Questionnaires
13.
Acta Psychol (Amst) ; 191: 261-270, 2018 Nov.
Article in English | MEDLINE | ID: mdl-30352360

ABSTRACT

In our study, we aimed to reduce bodily self-consciousness using a multisensory illusion (MI), and tested whether this manipulation increases Self-objectification (the psychological attitude to perceive one's own body as an object). Participants observed their own body from a first-person perspective, through a head-mounted display, while receiving incongruent (or congruent) visuo-tactile stimulation on their abdomen or arms. Results showed stronger feelings of disownership, loss of agency and sensation of being out of ones' own body during incongruent compare to congruent stimulation. This reduced bodily self-consciousness did not affect Self-objectification. However, self-objectification (as measured by the appearance of control beliefs subscale of the Objectified Body Consciousness questionnaire) was positively correlated with the MI strength. Moreover, we investigated the impact of MI and Self-objectification on body size estimation. We found systematic body size underestimation, irrespective of type of stimulation or tendency to Self-objectification. These results document a simple yet effective approach to alter bodily self-consciousness, which however spare Self-objectification and body size-perception.


Subject(s)
Body Image , Emotions/physiology , Illusions/physiology , Self Concept , Touch/physiology , Visual Perception/physiology , Adult , Body Image/psychology , Body Size/physiology , Consciousness/physiology , Female , Humans , Illusions/psychology , Photic Stimulation/methods , Size Perception/physiology , Surveys and Questionnaires , Young Adult
14.
Exp Brain Res ; 236(12): 3391-3403, 2018 Dec.
Article in English | MEDLINE | ID: mdl-30267139

ABSTRACT

Considering the wealth of recent studies on affective touch, to date, little research addressed the role of the other sensory modalities in the modulation of hedonic tactile perception. Here, we investigated the behavioral and electrodermal signature of the interaction between simultaneously presented visual and tactile stimuli. In three experiments, participants were presented with emotional pictures (international affective picture system; IAPS), while their forearm was gently stroked by means of different tactile textures (i.e., sandpaper, satin, tinfoil, abrasive sponge, and skin-to-skin contact). In Experiment 1, the participants evaluated the pleasantness of the tactile stimulation received, while in Experiment 2 they evaluated the pictures emotional valence. In Experiment 3 the participants rated the pleasantness, the smoothness and the softness of the textures; skin conductance responses (SCRs) were also measured. In sum, the results revealed that while the visual valence ratings were not modulated by the tactile stimulation, the hedonic and sensory tactile ratings were modulated by the visual presentation of both positively and negatively valenced pictures, as well as by neutral pictures. The modulatory effects occurring during visuo-tactile interactions might thus be not necessarily reciprocal. Moreover, the SCRs were not differently affected by the visuo-tactile or tactile conditions of stimulus presentation, suggesting a dissociation between behavioral and electrodermal effects in multisensory interactions.


Subject(s)
Arm/physiology , Emotions/physiology , Galvanic Skin Response/physiology , Photic Stimulation , Physical Stimulation , Touch Perception/physiology , Adult , Female , Humans , Male , Pleasure , Psychomotor Performance/physiology , Recognition, Psychology/physiology , Sensation , Young Adult
15.
Multisens Res ; 31(5): 351-371, 2018 Jan 01.
Article in English | MEDLINE | ID: mdl-31264602

ABSTRACT

Audition and touch interact with one another and share a number of similarities; however, little is known about their interplay in the perception of temporal duration. The present study intended to investigate whether the temporal duration of an irrelevant auditory or tactile stimulus could modulate the perceived duration of a target stimulus presented in the other modality (i.e., tactile or auditory) adopting both a between-participants (Experiment 1) and a within-participants (Experiment 2) experimental design. In a two-alternative forced-choice task, participants decided which of two events in a target modality was longer. The simultaneously distractor stimuli were presented with a duration that was either congruent or incongruent to the target's. Results showed that both the auditory and tactile modalities affected duration judgments in the incongruent condition, decreasing performance in both experiments. Moreover, in Experiment 1, the tactile modality enhanced the perception of auditory stimuli in the congruent condition, but audition did not facilitate performance for the congruent condition in the tactile modality; this tactile enhancement of audition was not found in Experiment 2. To the best of our knowledge, this is the first study documenting audiotactile interactions in the perception of duration, and suggests that audition and touch might modulate one another in a more balanced manner, in contrast to audiovisual pairings. The findings support previous evidence as to the shared links and reciprocal influences when audition and touch interact with one another.

16.
Multisens Res ; 31(6): 501-522, 2018 Jan 01.
Article in English | MEDLINE | ID: mdl-31264615

ABSTRACT

Despite the large number of studies on the multisensory aspects of tactile perception, very little is known regarding the effects of visual and auditory sensory modalities on the tactile hedonic evaluation of textures, especially when the presentation of the stimuli is mediated by a haptic device. In this study, different haptic virtual surfaces were rendered by varying the static and dynamic frictional coefficients of a Geomagic® Touch device. In Experiment 1, the haptic surfaces were paired with pictures representing everyday materials (glass, plastic, rubber and steel); in Experiment 2, the haptic surfaces were paired with sounds resulting from the haptic exploration of paper or sandpaper. In both the experiments, participants were required to rate the pleasantness and the roughness of the virtual surfaces explored. Exploration times were also recorded. Both pleasantness and roughness judgments, as well as the durations of exploration, varied as a function of the combinations of the visuo-tactile and the audio-tactile stimuli presented. Taken together, these results suggest that vision and audition modulate haptic perception and hedonic preferences when tactile sensations are provided through a haptic device. Importantly, these results offer interesting suggestions for designing more pleasant, and even more realistic, multisensory virtual surfaces.

17.
Perception ; 46(12): 1356-1370, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28718747

ABSTRACT

Recent findings have shown that sounds improve visual detection in low vision individuals when the audiovisual stimuli pairs of stimuli are presented simultaneously and from the same spatial position. The present study purports to investigate the temporal aspects of the audiovisual enhancement effect previously reported. Low vision participants were asked to detect the presence of a visual stimulus (yes/no task) presented either alone or together with an auditory stimulus at different stimulus onset asynchronies (SOAs). In the first experiment, the sound was presented either simultaneously or before the visual stimulus (i.e., SOAs 0, 100, 250, 400 ms). The results show that the presence of a task-irrelevant auditory stimulus produced a significant visual detection enhancement in all the conditions. In the second experiment, the sound was either synchronized with, or randomly preceded/lagged behind the visual stimulus (i.e., SOAs 0, ± 250, ± 400 ms). The visual detection enhancement was reduced in magnitude and limited only to the synchronous condition and to the condition in which the sound stimulus was presented 250 ms before the visual stimulus. Taken together, the evidence of the present study seems to suggest that audiovisual interaction in low vision individuals is highly modulated by top-down mechanisms.


Subject(s)
Sound Localization/physiology , Vision Disparity/physiology , Vision, Low/physiopathology , Visual Perception/physiology , Acoustic Stimulation/methods , Adult , Aged , Female , Humans , Male , Middle Aged , Photic Stimulation/methods , Reaction Time , Young Adult
18.
Front Hum Neurosci ; 11: 291, 2017.
Article in English | MEDLINE | ID: mdl-28634447

ABSTRACT

Functional movement disorders (FMD) are characterized by motor symptoms (e.g., tremor, gait disorder, and dystonia) that are not compatible with movement abnormalities related to a known organic cause. One key clinical feature of FMD is that motor symptoms are similar to voluntary movements but are subjectively experienced as involuntary by patients. This gap might be related to abnormal self-recognition of bodily action, which involves two main components: sense of agency and sense of body ownership. The aim of this study was to systematically investigate whether this function is altered in FMD, specifically focusing on the subjective feeling of agency, body ownership, and their interaction during normal voluntary movements. Patients with FMD (n = 21) and healthy controls (n = 21) underwent the moving Rubber Hand Illusion (mRHI), in which passive and active movements can differentially elicit agency, ownership or both. Explicit measures of agency and ownership were obtained via a questionnaire. Patients and controls showed a similar pattern of response: when the rubber hand was in a plausible posture, active movements elicited strong agency and ownership; implausible posture of the rubber hand abolished ownership but not agency; passive movements suppressed agency but not ownership. These findings suggest that explicit sense of agency and body ownership are preserved in FMD. The latter finding is shared by a previous study in FMD using a static version of the RHI, whereas the former appears to contrast with studies demonstrating altered implicit measures of agency (e.g., sensory attenuation). Our study extends previous findings by suggesting that in FMD: (i) the sense of body ownership is retained also when interacting with the motor system; (ii) the subjective experience of agency for voluntary tapping movements, as measured by means of mRHI, is preserved.

19.
PLoS One ; 11(12): e0168489, 2016.
Article in English | MEDLINE | ID: mdl-27977783

ABSTRACT

In the rubber hand illusion (RHI), watching a rubber hand being stroked in synchrony with one's own hidden hand may induce a sense of ownership over the rubber hand. The illusion relies on bottom-up multisensory integration of visual, tactile, and proprioceptive information, and on top-down processes through which the rubber hand is incorporated into pre-existing representations of the body. Although the degree of illusory experience varies largely across individuals, the factors influencing individual differences are unknown. We investigated whether sensory suggestibility might modulate susceptibility to the RHI. Sensory suggestibility is a personality trait related to how individuals react to sensory information. Because of its sensory nature, this trait could be relevant for studies using the RHI paradigm. Seventy healthy volunteers were classified by Sensory Suggestibility Scale (SSS) scores as having high or low suggestibility and assigned to either a high- (High-SSS) or a low-suggestibility (Low-SSS) group. Two components of the RHI were evaluated in synchronous and asynchronous stroking conditions: subjective experience of sense of ownership over the rubber hand via a 9-statement questionnaire, and proprioceptive drift as measured with a ruler. The High-SSS group was generally more susceptible to the subjective component; in the synchronous condition, they rated the statement assessing the sense of ownership higher than the Low-SSS group. The scores for this statement significantly correlated with the total SSS score, indicating that the higher the sensory suggestibility, the stronger the sense of ownership. No effect of sensory suggestibility on proprioceptive drift was observed, suggesting that the effect is specific for the subjective feeling of ownership. This study demonstrates that sensory suggestibility may contribute to participants' experience of the illusion and should be considered when using the RHI paradigm.


Subject(s)
Hand/physiology , Illusions/physiology , Rubber , Self Concept , Visual Perception/physiology , Female , Healthy Volunteers , Humans , Male , Proprioception/physiology , Surveys and Questionnaires , Touch Perception/physiology
20.
Multisens Res ; 29(1-3): 133-55, 2016.
Article in English | MEDLINE | ID: mdl-27311294

ABSTRACT

Over the last decade, scientists working on the topic of multisensory integration, as well as designers and marketers involved in trying to understand consumer behavior, have become increasingly interested in the non-arbitrary associations (e.g., sound symbolism) between different sensorial attributes of the stimuli they work with. Nevertheless, to date, little research in this area has investigated the presence of these crossmodal correspondences in the tactile evaluation of everyday materials. Here, we explore the presence and nature of the associations between tactile sensations, the sound of non-words, and people's emotional states. Samples of cotton, satin, tinfoil, sandpaper, and abrasive sponge, were stroked along the participants' forearm at the speed of 5 cm/s. Participants evaluated the materials along several dimensions, comprising scales anchored by pairs of non-words (e.g., Kiki/Bouba) and adjectives (e.g., ugly/beautiful). The results revealed that smoother textures were associated with non-words made up of round-shaped sounds (e.g., Maluma), whereas rougher textures were more strongly associated with sharp-transient sounds (e.g., Takete). The results also revealed the presence of a number of correspondences between tactile surfaces and adjectives related to visual and auditory attributes. For example, smooth textures were associated with features evoked by words such as 'bright' and 'quiet'; by contrast, the rougher textures were associated with adjectives such as 'dim' and 'loud'. The textures were also found to be associated with a number of emotional labels. Taken together, these results further our understanding of crossmodal correspondences involving the tactile modality and provide interesting insights in the applied field of design and marketing.


Subject(s)
Association , Emotions/physiology , Language , Touch Perception/physiology , Adult , Auditory Perception , Female , Humans , Male , Sound , Symbolism , Young Adult
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